ii The Latins 25 immediately after the overthrow of the Tarquins Rome made a commercial treaty with Carthage, in which she stands forth as the most important city of Latium. The connexion with Carthage was inherited from the Etruscans. But the general drift of her foreign policy was now different: her relations with her Etruscan neighbours were strained, and she devoted herself to developing her influence in Latium. Tradition testifies to the formation of a league, political as well as religious, between seven Latin cities, as early as the time of Etruscan domination. Rome was not a member of that league; and her subsequent adhesion to it is a clear proof of the steady consolidation of strength, to enable Latium to cope with her neighbours. The systematic colonization of lands taken from those neighbours served to spread the limits of the league. This course of events in Latium finally arrested the south- ward movement of the Etruscans. They lost hold of Cam- pania as soon as Latium started an independent foreign policy, and all its considerable cities, Rome included, ceased to be members of the Etruscan league. It is probable that what had happened at Rome was happening in other out- lying parts of the Etruscan nation. Connexion between the different parts of the league was relaxed, and in remote places the native inhabitants asserted themselves and ousted their Etruscan conquerors, as they had in Latium. Thus in the valley of the Po, for instance, at Bononia (the modern Bologna), and in Umbria, the local element now came to the front. This would account for the successful invasion of the north by the Celts or Gauls, the last immigrants of Indo-European stock. It is certain that the Celts appeared in Italy not later than the fifth century B. c.; and they occupied by degrees almost all the Po valley, except the country of the Veneti and a con- siderable part of Umbria. Their appearance on the scene confined the political operations of Etruria in Italy to very modest dimensions: she was cut off from the south by the Latins and from the north by the Gauls ; and it was likely that both these nations would before long proceed to attack her.